Radiopharmaceuticals In Nuclear Medicine Research Articles

Synthesis of the European ALARA network 20th workshop ‘ALARA for interventional radiology and nuclear medicine’

The European as low as reasonably achievable(ALARA) network regularly organises workshops on topical issues in radiation protection (RP). The topic of the 20th workshop was: ‘ALARA for interventional radiology (IR) and nuclear medicine (NM)’. The objective was to examine the challenges faced when applying the optimisation principle (ALARA) in IR and NM and to consider how ALARA could be better implemented for patient and staff exposures. This memorandum provides a synthesis of the workshop sessions, and recommendations coming from the working groups discussion. Parallels are drawn with the recommendations arising from the 13th EAN workshop on ‘ALARA and the medical sector (2011)’ to consider how the optimisation challenges in IR and NM have evolved over the past decade. Current levels of exposure are presented along with operational practice and the challenges and opportunities for improvement, both in monitoring and practice. Whilst RP challenges remain, the application of ALARA appears more established in IR compared with experiences reported in 2011. The application of ALARA to emerging technologies in the NM setting is in need of further development to ensure that RP is considered at all stages in the development process of new radiopharmaceuticals. Besides the obvious technical and operational aspects, the importance of education and training, human factors and broadly the RP ‘culture’ were deemed fundamental to the success of the application of ALARA and where further emphasis is needed. All concerned parties, medical physics experts (MPEs), radiation protection experts, clinical staff, manufacturers and regulators have a role to play in the application of ALARA and this is discussed in the memorandum. Many of the recommendations from the 13th EAN workshop remain applicable today and overlap with the recommendations arising from the 20th workshop. This should prompt attention given that the use of IR and the development of novel radiopharmaceuticals for NM is only anticipated to increase with time.

Evaluation of the contamination droplet model used for the assessment of skin dose during the manipulation of radiopharmaceuticals

The manipulation of radiopharmaceuticals in nuclear medicine can result in the droplet contamination of operators resulting in the accumulation of a significant skin dose. Current methods to estimate this skin dose often utilise a 50 μl cylindrical droplet model, which can lead to unrealistically high estimated skin doses for some radiopharmaceuticals. By conducting experiments to measure the volume of real droplets arising from simulating the manipulation of radiopharmaceuticals, this work found that 50 μl is an overestimation of a realistic contamination droplet. For almost all radiopharmaceuticals considered in this work, incorporating a smaller droplet volume into skin dose simulations resulted in higher estimates of skin dose rate per unit of activity, which, when combined with appropriate activity concentrations and droplet volumes, resulted in lower skin doses for contamination droplet incidents. The results presented in this work challenge the 50 μl contamination droplet volume and highlight the importance of having an accurate model when estimating the skin dose for contamination scenarios.

131I-Labeled Anti-HER2 Nanobody for Targeted Radionuclide Therapy of HER2-Positive Breast Cancer.

The unique structure of nanobodies is advantageous for the development of radiopharmaceuticals for nuclear medicine. Nanobodies targeted to human epidermal growth factor receptor 2 (HER2) can be used as tools for the imaging and therapy of HER2-overexpressing tumors. In this study, we aimed to describe the generation of a 131I-labeled anti-HER2 nanobody as a targeted radionuclide therapy (TRNT) agent for HER2-positive breast cancer. The anti-HER2 nanobody NM-02 was labeled with 131I using the iodogen method, and its radiochemical purity and stability in vitro were assessed. The pharmacokinetic profile of 131I-NM-02 was investigated in normal mice. Tumor accumulation, biodistribution, and therapeutic potential of 131I-NM-02 were evaluated in HER2-positive SKBR3 xenografts; HER2-negative MB-MDA-231 xenografts were used as the control group. 131I-NM-02 could be readily prepared with satisfactory radiochemical purity and stability in vitro. Apparent tumor uptake was observed in HER2-positive tumor-bearing mice with rapid blood clearance and favorable biodistribution. 131I-NM-02 could significantly inhibit tumor growth and extend the life of these mice with good organ compatibility. Negligible tumor accumulation and inhibitory effects of 131I-NM-02 were observed in the negative control group. 131I-NM-02 has the potential to be explored as a novel tool for TRNT of HER2-positive breast cancer.

Various Aspects of Fasting on the Biodistribution of Radiopharmaceuticals.

It is demonstrated that fasting can alter the biodistribution of radiopharmaceuticals in nuclear medicine. Various studies have highlighted that fasting is interpreted to be easy for physicians during PET study, fasting is one of the most important factors determining the usefulness of this protocol. It is well documented that fasting can suppress normal 18F-FDG PET uptake during nuclear cardiology. However, there is no consensus about the usefulness of fasting on radiopharmaceuticals, especially on 18F-FDG in PET imaging, but special attention should be paid to the setting of the fasting duration. Nevertheless, it does seem we still need extensive clinical studies in the future. The present study aims to review the various aspects of fasting, especially metabolic alteration on radiopharmaceutical biodistribution. In this study, we focused more on the effect of fasting on 18F-FDG biodistribution, which alters its imaging contrast in cardiology and cancer imaging. Therefore, shifting substrate metabolism from glucose to free fatty acids during fasting can be an alternative approach to suppress physiological myocardial uptake.

Need for harmonisation of extremity dose monitoring in nuclear medicine: results of a survey amongst national dose registries in Europe

Staff handling radiopharmaceuticals in nuclear medicine (NM) may receive significant extremity doses. Over the last decade in particular there has been an increase in NM procedures and new radiopharmaceuticals have been introduced. However, literature provides limited recent data on the exposure of the extremities. In addition, proper assessment of the equivalent dose to the skin can be difficult when applied to the fingertips. In order to gain insight in the actual exposure and to find out how European countries are dealing with monitoring of the extremities, a survey was performed amongst European regulatory authorities. The questions covered general aspects of the national dose registries (NDRs), the measured extremity doses and the practice of the monitoring of workers. The survey shows that extremity dosimetry is performed for about 25%–50% of the monitored workers in NM. Also, the recorded extremity doses in the NDRs are low (mean values 5–29 mSv yr−1) compared to the dose limit. Despite the recommendations that have been published in the last 10 years, few countries provide guidance on the wearing position of extremity dosemeters and the correction factor to estimate the maximum equivalent skin dose from the measured dose. This may lead to an underestimation of the maximum skin dose. Thermoluminescence ring dosemeters are widely used, but wrist dosemeters are also very common, even though the correlation of the measurement with the maximum skin dose is worse than for ring dosemeters. Furthermore, not all countries had a central registration of the extremity dose at the time the survey was performed.

Pharmacological activities and potential use of bovine colostrum for peptide-based radiopharmaceuticals: A review

Bovine colostrum (BC) is the initial milk produced by cows after giving birth. It has been used to treat human diseases, such as infections, inflammations, and cancers. Accumulating evidence suggests that bovine lactoferrin and bovine antibodies seem to be the most important bioactive constituents in BC. Thus, BC has also been reviewed for its potential to deliver short-term protection against coronavirus disease 2019 (COVID-19). In addition, it can potentially be explored as a precursor for peptide-based radiopharmaceuticals. To date, several bioactive peptides have been isolated from BC, including casocidin-1, casecidin 15 and 17, isracidin, caseicin A, B, and C. Like other peptides, bioactive peptides derived from BC could be used as a valuable precursor for radiopharmaceuticals either for diagnosis or therapy purposes. This review provides bovine colostrum’s biological activities and a perspective on the potential use of peptides from BC for developing radiopharmaceuticals in nuclear medicine.

Innovative Radiopharmaceuticals for Cancer Diagnosis and Treatment

The presented material summarizes the experience of Cancer Research Institute and Tomsk Polytechnical University team in the development of original radiopharmaceuticals (RP) for nuclear medicine. The first such unique for world nuclear medicine RP was a Thallium­199. The Thallium­199 is successfully used for breast cancer diagnosis and its lymphogenous metastasis, as well as to visualize cancer of the larynx and laryngopharynx, their relapses and for differential diagnosis of inflammatory and tumor processes of the musculoskeletal system. The great practical importance for nuclear medicine has the organization of a waste­free production of sorption and extraction generators of Technetium­-99m at the IRT­T TPU nuclear research reactor, as well as the creation of a fully automated 99mTc module operating on a waste­ free technology. The development of the 99mTc­Alotech for targeting imaging of sentinel lymph nodes (SLN) has also great importance for clinical oncology. The main advantage of 99mTc­Glucoscin is that metabolic tumor imaging with the innovative RP use can be performed using a conventional gamma camera, which significantly reduces the cost of the diagnostic procedure. The present and promising developments of the research teams of the Tomsk Scientific Research Center and the Tomsk Polytechnic University are closely related to theranostics — the use of RPs obtained on the basis of same target compound labeled with different isotopes intended for the diagnosis or therapy of oncological diseases.

Theragnostic Aspects and Radioimmunotherapy in Pediatric Tumors.

The use of theragnostic radiopharmaceuticals in nuclear medicine has grown rapidly over the years to combine the diagnosis and therapy of tumors. In this review, we performed web-based and desktop literature research to investigate and explain the potential role of theragnostic imaging in pediatric oncology. We focused primarily on patients with aggressive malignancies such as neuroblastoma and brain tumors, to select patients with the highest chance of benefit from personalized therapy. Moreover, the most critical and groundbreaking applications of radioimmunotherapy in children’s oncology were examined in this peculiar context. Preliminary results showed the potential feasibility of theragnostic imaging and radioimmunotherapy in pediatric oncology. They revealed advantages in the management of the disease, thereby allowing an intra-personal approach and adding new weapons to conventional therapies.

Synthesis and properties of Cu- and Pd-complexes of cyclen conjugates with pheophorbide and bacteriopheophorbide

Objectives. Chlorin and bacteriochlorin photosensitizers are effective agents for cancer photodynamic therapy and fluorescence imaging. They are also excellent chelators forming stable metal complexes. Besides, 64 Cu and 109 Pd isotopes can serve as emitters for nuclear medicine. Chelation of these metals with cyclen conjugates with chlorin and bacteriochlorin photosensitizers can become a simple and universal strategy for the synthesis of diagnostic and therapeutic radiopharmaceuticals for nuclear medicine. This article reports on the synthesis of similar Cu and Pd complexes of cyclen conjugates with pheophorbide and bacteriopheophorbide and the study of their photophysical properties. Methods. Metalation of cyclen conjugates was carried out with palladium and copper acetates. For bacteriochlorins, 6-O-palmitoyl-L-ascorbic acid was additionally used as a reducing agent. MALDI mass spectrometry, which was carried out on a time-of-flight mass spectrometer Bruker Ultraflex TPF/TOF and a Bruker Daltonics Autoflex II confirmed the structure of the compounds obtained Electronic absorption spectra were obtained on a Shimadzu 3101 spectrophotometer. Fluorescence and phosphorescence spectra were obtained on a FluoTime 300 PicoQuant spectrofluorometer. Results. Photophysical studies of metal complexes showed that the introduction of palladium cations quenches fluorescence and increases the quantum yield of singlet oxygen generation to 0.98 for the chlorin conjugate. Besides, it decreases the quantum yield of fluorescence to 0.10 and increases the quantum yield of singlet oxygen generation to 0.72 for the bacteriochlorin conjugate. Introducing a copper cation to cyclen conjugates with pheophorbide and bacteriopheophorbide leads to photophysical characteristics quenching. Conclusions. Due to the stability of the synthesized metal complexes in acidic media, as well as the short metalation time (5, 20, 10, and 15 minutes) it is reasonable to expect the successful development of effective imaging agents for positron emission tomography and radionuclide therapy. In addition, the residual fluorescence of bacteriochlorins makes it possible to use fluorescence diagnostics in combination with these methods.

The substantiation of the quality control method for determining the radionuclide purity and the total radioactivity of radiopharmaceuticals

The quality control in the manufacture of radiopharmaceuticals has a prominent role in providing the supply of high-quality drugs for the diagnosis and treatment of patients with cancer. It has been determined that the permission to use radiopharmaceuticals directly depends on the results of the analytical control. Aim. To reduce the time for the quality control of radiopharmaceuticals, resulting in both the radiochemical yield of the product and its specific activity. This is an important parameter in conducting diagnostic or therapeutic procedures. Materials and methods. To optimize the process of the quality control for radiopharmaceuticals we propose to replace the following laboratory equipment: a Moleculer Mol gamma spectrometer, which monitors the radionuclide purity of radiopharmaceuticals (gamma-ray energy measurement) and a BIODEX ATOMLAB 500 preloaded device (measurement of the total radioactivity of a drug) to a radionuclide calibrator for nuclear medicine developed by domesti scientists of the Institute of Scintillation Materials and made at the “Kvant” X-ray equipment plant in Kharkiv. Results and discussion. It has been proven that the use of calibrator radiopharmaceuticals for nuclear medicine should be applied as the quality control. It has been substantiated that the calibrator of doses for nuclear medicine performs two functions simultaneously. Conclusions. The method of optimization of the quality control of radiopharmaceuticals using the device – a radionuclide calibrator for nuclear medicine allows us to simultaneously obtain the results of the analysis by such indicators as “radionuclide purity” and “radioactivity”.

Mechanical design of the superconducting solenoid package for the SARAF-linac project

The Soreq Applied Research Accelerator Facility (SARAF) in Israel will provide an intense source of fast neutrons and radioactive nuclei for neutron applications, to explore rare nuclear reactions and produce new types of radiopharmaceuticals for nuclear medicine. CEA Paris-Saclay is in charge of the design, construction and commissioning of this superconducting linear particle accelerator (linac) to produce the first particle beams in 2022.The superconducting linac is part of the SARAF accelerator and it will be equipped with twenty identical solenoid packages arranged in four 5-metre long cryomodules; they are located between the cavities and they ensure the beam control. The solenoid package is a complex mechanical system and it is designed to operate at cryogenic temperatures. It comprises the main solenoid coil with an integrated square flux density of 3.5 T2 m , two lateral shielding coils to reduce the fringe fields on the cavities as well as two pairs of steering coils. This ensemble is enclosed in a stainless steel helium vessel.In this study, we present the mechanical design of the first prototype of the solenoid package with a particular focus on the main coil, whereby the superconducting wire (Nb–Ti/Cu) is wound and cured on two extremity flanges made of epoxy reinforced with glass cloth (G-10). The modelling of the solenoid components is carried out using Finite Element Analysis (FEA) and the results of simulations are used to assess the structural integrity of the components. Moreover, an extensive literature review is conducted to collect the mechanical properties at cryogenic temperature of the composite materials used for the construction. Finally, the results of the experimental validation of the first solenoid prototype are presented. The experimental campaign is carried out using a cryostat designed on purpose to reproduce both the final operating temperature and magnetic field.

Radionuclides: medicinal products or rather starting materials?

The EU directive 2001/83 describes the community code for medicinal products for human use including radiopharmaceuticals. In its current definition, also radionuclide precursors, such as fluorine-18, need to hold a marketing authorization before being placed on the market. The potential of novel radiopharmaceuticals for nuclear medicine is, although encouraged by European legislation and its respective guidance documents, therefore hampered by the regulatory framework. An update of EU directive 2001/83 would be beneficial for the development of novel radiopharmaceuticals and a safe advance in nuclear medicine.

О подготовке кадров для ядерной медицины

Purpose: Due to the necessity of improving the education of medical workers it is vital to conduct a review of the current state of training for work associated with the use of high-tech equipment and the use of radiopharmaceuticals for nuclear medicine.
 Results: To ensure the availability of modern, high-quality medical care, oriented to world standards, it should be considered that the necessary conditions are based not only on the development of medical science and technology, material and technical equipment, but also on the provision of highly qualified personnel with a certain set of competencies.
 Currently, the training and professional development of personnel for this area is carried out at all levels of vocational education: secondary and higher in accordance with the Lists of specialties and areas of vocational education. At the same time, the issues of developing and approving relevant professional standards and Federal state educational standards (FSES) for the needs of nuclear medicine remain unsolved, which in turn is one of the factors that reduce the demand for specialists in this field in the labor market.
 At the same time, the issues of developing and approving relevant professional standards and FSES for the needs of nuclear medicine remain unsolved, which in turn is one of the factors that reduce the demand for specialists in this field on the labor market.
 The personnel crisis is overcome due to the implementation of additional professional programs and practical training at the bases of leading scientific, clinical and educational institutions that are leaders in the field of nuclear medicine and radiopharmaceuticals.
 Conclusion: In order to address the shortage of personnel for such a booming industry, a clear coordinated plan is needed, which would include systematic measures to train personnel both at the undergraduate level and to improve already prepared specialists. In addition, it is necessary to prepare a pool of highly qualified faculty for training specialists of a new formation. It is necessary to create federal educational standards taking into account that the current state of medical science and on the basis of professional standards. Work in this direction can be successful only if all stakeholders are actively involved: educational organizations, the professional community and government structures.
 At the same time, it is an obvious fact that, before the adoption of professional standards and the FSES, the available experience of leading scientific and educational organizations in the training of specialists should be adopted and they should receive support and development.

Neuroendocrine differentiation in castration resistant prostate cancer. Nuclear medicine radiopharmaceuticals and imaging techniques: A narrative review.

Androgen Deprivation Therapy (ADT) is the primary treatment for patients suffering from relapsing or advanced prostate cancer (PC). Hormone therapy generally guarantees adequate clinical control of the disease for some years, even in those patients affected by widespread skeletal and soft tissue metastases. Despite ADT, however, most patients treated with hormones eventually progress to castration-resistant prostate cancer (CRPC), for which there are no effective treatments. This clinical reality is an open challenge to the oncologist because of those neoplasms which elaborate neuroendocrine differentiation (NED). An online search of current and past literature on NED in CRPC was performed. Relevant articles dealing with the biological and pathological basis of NED, with nuclear medicine imaging in CRPC and somatostatin treatment in NED were analyzed. NED may arise in prostate cancer patients in the late stages of ADT. The onset of NED offers prognostic insight because it reflects a dramatic increase in the aggressive nature of the neoplasm. Several genetic, molecular, cytological and immunohistochemical markers are associated with this transformation. Among these, overexpression of somatostatin receptors, seen through Nuclear Medicine testing, is one of the most studied. Preliminary studies show that the overexpression of somatostatin receptors related to NED in CRPC may easily be studied in vivo with PET/CT. This finding offers a potentially useful objective for targeted therapy in CRPC. If the overexpression of SSTRs is shown to afflict a significant segment of patients with CRPC, this will open further study of possible therapeutic options based on this marker.

93. Estimation of doses to the extremities during manipulation of radiopharmaceuticals in nuclear medicine: A Monte Carlo calculation approach in realistic geometric lay-outs

Purpose The aim of this study was to introduce a calculation approach, based on a simple and user-friendly interface to Monte Carlo simulation, for the estimation of the radiation dose to the extremities of the personnel professionally exposed to the ionizing radiations emitted by radionuclides employed in nuclear medicine. Methods Monte Carlo simulations in GAMOS (GEANT4-based Architecture for Medicine-Oriented Simulations) were carried out for 18F, 68Ga, 90Y, 99mTc, 111In, 131I and 177Lu nuclides in water solutions enclosed either in glass or in plastic receptacles, such as vials or syringes of different sizes and filling fractions. Superficial and deep dose equivalents were estimated, around the lateral surface of the receptacle, at different distances. A comparison was made with the results from VARSKIN 5.3, which were computed in the standard VARSKIN geometric lay-out of a volume source. Results Skin and deep dose equivalents, at 70 μm and 1 cm of depth, are reported for all the considered configurations, highlighting the importance of adopting a realistic geometrical configuration. The comparison made between the average exposition below the source bottom, computed through VARSKIN, and the maximum exposition on the lateral surface at the source middle plane, evaluated by Monte Carlo simulations, reveals a qualitative agreement for a limited number of configurations only, since the different geometries affect the dose deposited in the scoring volumes. A further source of disagreement is related to the deterministic approach in which electron energy deposition is treated in VARSKIN and its influence in proximity of electron maximum range, and to the absence of bremsstrahlung emission. Another source of discrepancy, for some nuclides, is the difference in radionuclide emission spectra. Conclusions Due to the easiness of implementation of GAMOS simulations, case-specific realistic geometries and nuclides can be adopted and results can be obtained in very reasonable computation times.

In vivo Exposure Effects of 99mTc-methoxyisobutylisonitrile on the FDXR and XPA Genes Expression in Human Peripheral Blood Lymphocytes.

Objective(s):In recent years, the application of radiopharmaceuticals in nuclear medicine has increased substantially. Following the diagnostic procedures performed in nuclear medicine departments, such as myocardial perfusion imaging, patients generally receive considerable doses of radiation. Normally, radiation-induced DNA damages are expected following exposure to a low-dose ionizing radiation. In order to detect molecular changes, high-sensitivity techniques must be utilized. The aim of this study was to assess the effect of a low-dose (below 10 mSv) gamma ray on gene expression using quantitative real-time polymerase chain reaction (qRT-PCR).Methods:Blood samples were obtained from 20 volunteer patients who underwent myocardial perfusion imaging. They were given various doses of Technetium-99m methoxyisobutylisonitrile (99mTc-MIBI). After that, peripheral blood mononuclear cells (PBMNs) were derived, and then total RNA was extracted and reverse-transcribed to cDNA. Finally, the expression levels of xeroderma pigmentosum complementation group-A (XPA) and ferredoxin reductase (FDXR) genes were determinded through qRT-PCR technique using SYBR Green.Results:XPA and FDXR expression levels were obtained following a very low-dose ionizing radiation. A significant up-regulation of both genes was observed, and the gene expression level of each individual patient was different. If differences in the administered activity and radiosensitivity are taken into account, the observed differences could be justified. Furthermore, gender and age did not play a significant role in the expression levels of the genes under study.Conclusion:The up-regulation of FDXR after irradiation revealed the high-sensitivity level of this gene; therefore, it could be used as an appropriate biomarker for biological dosimetry. On the other hand, the up-regulation of XPA is an indication of DNA repair following radiation exposure. According to linear no-threshold model (LNT) and the results obtained from this study, a very low dose of ionizing radiation could bring about adverse biological effects at molecular level in the irradiated person.

Randomized Controlled Trials for Diagnostic Imaging: Conceptual and Pratical Problems

We raise a problem of applicability of RCTs to validate nuclear diagnostic imaging tests. In spite of the wide application of PET and other similar techniques that use radiopharmaceuticals for diagnostic purposes, RCT-based evidence on their validity is sparse. We claim that this is due to a general conceptual problem that we call Prevalence of Treatment, which arises in connection with designing RCTs for testing any diagnostic procedure in the present context of medical research, and is particularly apparent in this case. We also identify three practical reasons why RCTs do not qualify as the best option for PET validation, which have to do with specific characteristics of nuclear diagnostic imaging, and of radiopharmaceuticals. The paper is meant to contribute both to the philosophical discussion on the EBM hierarchy of evidence, and on the specific debate on radiopharmaceuticals in nuclear medicine.

Current Trends in Radio-Pharmaceuticals

The development of radiotraces with defined affinities for specific receptor systems is a potentially useful approach to the design of radio pharmaceuticals for nuclear medicine. Radio labeled ligands, such as hormones and neurotransmitters, are being synthesized and evaluated as diagnostic tools for diseases which can be characterized either by changes in receptor concentration or by novel receptor expression. Since the utility of a radio pharmaceutical is dependent upon the achievement of adequate ratios of target to non-target accumulation of radio activity, design of radio traces via the receptor approach attempts to exploit those systems in which receptor is present in significantly higher concentration at potential target sites such as tumors. Receptormediated radio tracers are also currently being used in animal models to investigate the normal tissue distribution of drug and hormone receptors and the in-vivo pharmacokinetics of receptor binding. The successful development of receptor-avid radiopharmaceuticals will depend upon the ability to synthesize ligands of high specific radio activity which retain the high affinity and binding specifically for the receptor after radio labeling.

Influence of the chelator structures on the stability of Re and Tc tricarbonyl complexes with iminodiacetic acid tridentate ligands: a computational study.

The development of novel radiopharmaceuticals for nuclear medicine based on M(CO)3 (M = Tc, Re) complexes has attracted great attention. The versatility of this core and the easy production of the fac-[M(CO)3(H2O)3](+) precursor could explain this interest. The main characteristics of these tricarbonyl complexes are the high substitution stability of the three CO ligands and the corresponding lability of the coordinated water molecules, yielding, via easy exchange of a variety of bi- and tridentate ligands, complexes xof very high kinetic stability. Here, a computational study of different tricarbonyl complexes of Re(I) and Tc(I) was performed using density functional theory. The solvent effect was simulated using the polarizable continuum model. These structures were used as a starting point to investigate the relative stabilities of tricarbonyl complexes with various tridentate ligands. These complexes included an iminodiacetic acid unit for tridentate coordination to the fac-[M(CO)3](+) moiety (M = Re, Tc), an aromatic ring system bearing a functional group (-NO2, -NH2, and -Cl) as a linking site model, and a tethering moiety (a methylene, ethylene, propylene butylene, or pentylene bridge) between the linking and coordinating sites. The optimized complexes showed geometries comparable to those inferred from X-ray data. In general, the Re complexes were more stable than the corresponding Tc complexes. Furthermore, using NH2 as the functional group, a medium length carbon chain, and ortho substitution increased complex stability. All of the bonds involving the metal center presented a closed shell interaction with dative or covalent character, and the strength of these bonds decreased in the sequence Tc-CO > Tc-O > Tc-N.

Comparison of surface contamination monitors for in vivo measurement of 131I in the thyroid

The routine handling of radiopharmaceuticals in nuclear medicine represents a significant risk of internal exposure to the staff. The IAEA recommends the implementation of monitoring plans for all workers subject to a risk of exposures above 1 mSv per year. However, in Brazil, such recommendation is practically unfeasible due to the lack of a sufficient number of qualified internal dosimetry services over the country. This work presents an alternative based on a simple and inexpensive methodology aimed to perform in vivo monitoring of 131I in the thyroid using portable surface contamination probes. Results show that all models evaluated in this work present enough sensitivity for the evaluation of accidental intakes.